The availability of local position determination units (PDUs), such as LORAN-C, and of global position determination systems, such as the Navstar Global Positioning System (GPS), for tracking locations and location observation times of a PDU antenna has produced a marked growth in the number of vehicle navigation systems available. These navigation systems are used to track a vehicle as the vehicle moves, or to plan a route to be followed by the vehicle.
Different approaches for route planning navigation systems are discussed in U.S. Pat. Nos. 5,262,775, 5,291,412, 5,291,413, 5,291,414 and 5,303,159, issued to Tamai et al, U.S. Pat. No. 5,311,414, issued to Tamai, Nos. 5,359,529 and 5,508,931, issued to Snider, U.S. Pat. No. 5,377,113, issued to Shibazaki et al, U.S. Pat. No. 5,414,630, issued to Oshizawa et al, U.S. Pat. No. 5,430,655, issued to Adachi, U.S. Pat. No. 5,515,283, issued to Desai et al, U.S. Pat. Nos. 5,544,060 and 5,550,538, issued to Fujii et al, and U.S. Pat. No. 5,523,950, issued to Peterson.
When a vehicle moves along roads, streets and highways (collectively referred to as "roads", the vehicle encounters two kinds of restrictions on vehicle maneuverability: traffic restrictions that are always present ("non-lapsing vehicle restrictions" or NLVRs) and traffic restrictions that vary with the time of day, with the day of the week, or with the season ("timed vehicle restrictions" or TVRs). Examples of the timed vehicle restrictions include No-Left-Turn, No-Right-Turn and No-U-Turn restrictions that are imposed during commute or rush hours, specially marked traffic lanes that can be used only by "car pool" vehicles (carrying two or three or more persons) during commute or rush hours, and side lanes that can be used for vehicle parking during portions of the day that are not commute or rush hours. This invention is concerned with timed turn restrictions ("TTRs") and timed lane restrictions ("TLRs"), which are restrictions on vehicle turns and/or on use of traffic lanes that vary with the time of day, with the day of the week and/or with the season.
In many of the navigation systems, a timed turn restriction is treated in the corresponding navigation database as a non-lapsing turn restriction so that a vehicle turn at the corresponding TTR location is never available. If the restriction on this turn is present at all hours except late evening hours, such as 10:00 p.m.-5:00 a.m., treatment of this TTR as a NLVR may have little effect on route planning. If the restriction on this turn is imposed only during a small portion of the daytime hours, such as 3:00-6:00 p.m., treatment of this TTR as a NLVR substantially penalizes or constrains the route planning process.
In navigation databases that account for the number of lanes available for vehicle traffic on a given segment of a road (referred to herein as a "link"), the presence of a timed lane restriction is often ignored, and the lane is treated as if it is unavailable for vehicle traffic in any direction. This approach also substantially penalizes or constrains the route planning process, especially if the lane is available for travel in the desired direction during some times with low or unsaturated traffic density. A pre-scheduled and temporary restriction on a vehicle turn or on use of a traffic lane may be treated as non-lapsing, which is too pessimistic, or as non-existent, which offers a rude surprise for any vehicle that includes that turn or link as part of its planned route.
If the presence of one or more timed vehicle restrictions is to be accurately accounted for, many questions should be first posed and answered. How can one obtain accurate local time? When and how should a TVR be included in a route planning process? How should the presence of a TVR be presented to a vehicle operator or user? How should diversion around a TVR, and route recalculation, be handled enroute? How should this diversion around a TVR be presented to the user? How should the occurrence of an unanticipated traffic incident, such as a traffic accident or temporary closing of a street or temporary imposition of turn restrictions at an intersection, be handled when the vehicle is enroute between the route origin or source and the route destination? Answers to these questions and to related questions should be incorporated in any robust navigation system that utilizes route planning and optimization.